Background Limited research exists on the use of portable, battery-powered cannabis vaporizers by adult e-cigarette users. Objective We assessed cannabis vaporization among adult e-cigarette users. Methods 522 adult vapers completed an online survey. Demographics; lifetime and past-month cannabis vaporization via e-cigarettes/vape-pens; preferences for hash oil, THC wax, or dried buds; and cannabis vaporization beliefs and motives were examined. Demographics, age of e-cigarette onset, e-cigarette use frequency, state-level legal status of cannabis, cannabis vaping beliefs/motives, and impulsivity were examined as predictors of lifetime cannabis vaporization, past-month cannabis vaporization, and cannabis vaping frequency. Results E-cigarette users reported lifetime (LT 17.8%) and past-month (PM 11.5%) cannabis vaporization. Vapers preferred hash oil (LT/PM 45.5/47.5%), THC wax (15.2/32.2%), and dried buds (39.4/35.6%). Cannabis vapers were motivated to vape cannabis because it tastes better (39.3/37.9%%), is healthier (42.9/39.7%%), is easier to conceal/hide (35.7/46.6%), does not smell as strong (42.9/39.7%), is more convenient (42.9/29.5%), and produces a stronger/better high (58.1/40.7%) than smoking cannabis. Lifetime and past-month cannabis vaporization, respectively, were associated with initiating e-cigarette use at an earlier age (OR = .090/0.88), being impulsive (OR = 2.25/3.23), having poor self-control (OR = 2.23/1.85), and vaporizing cannabis because it is easier to conceal/hide (OR = 2.45/2.48) or is more convenient than smoking cannabis (OR = 5.02/2.83). Frequency of vaping cannabis was associated with heavier e-cigarette use (ηp2 = 0.10) and impulsivity (ηp2 = 0.09). Conclusions Adult e-cigarette users are vaporizing cannabis using e-cigarettes and vape-pens. Use of these products should be monitored as they continue to gain popularity.